LED light source with better color mixing

ABSTRACT

A light source that has improved light mixing. The light source uses a nanolens layer in conjunction with an LED light source to enhance the mixing of the colored light emitting from the LED light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

TECHNICAL FIELD

The invention relates in general to a light-emitting diode light source,and is specifically a light-emitting diode light source that comprises ananolens layer in association with an encapsulated light emitting diodechip to improve light mixing.

BACKGROUND OF THE INVENTION

Light-emitting diodes generally emit light in a specific color or rangeof wavelengths. To produce a white light, it is usually necessary tocombine or mix the light from plural LEDs which emit different colors,for example, red, green and blue. Initially, light mixing wasaccomplished by placing LEDs of different colors next to each other suchthat the light emitted by each LED would mix with the light from theothers. A common structure associated with such mixing is a light guide

This approach has several drawbacks including poor color mixing, unevenlight intensity, and the presence of dark regions near the edges of thelight guide plate.

Several techniques have been made to improve the light mixing needed toproduce which light. One is the insertion of the LEDs into a mixingcavity within the light guide. Another is the use of a light diffusor tomix the colors. While these techniques have resulted in slightly bettercolor mixing, there remains a need for further improvement.

BRIEF SUMMARY OF THE INVENTION

An embodiment of the invention is a novel light emitting diode lightsource having an associated nanolens structure. The nanolens allows forimproved mixing of the light generated by the light-emitting diodescontained within the light source. Light mixing may be further enhancedthrough the use of a diffusant layer within the light source and/orreflectors placed adjacent to the diodes.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing, in which:

FIG. 1 is a cross-section of one embodiment of the invention;

FIG. 2 is a cross-section of an alternate embodiment of the invention;

FIG. 3 is a cross-section of a third embodiment of the invention; and

FIG. 4 is a cross-section of a fourth embodiment of the invention withits associated light guide.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an embodiment of the invention. In this embodiment, lightemitting diode chips 10 are attached to a substrate 11 and at leastpartially encapsulated with an encapsulant 12. Depending on the natureof the encapsulant 12, a casing 13 may be used to support theencapsulant 12. Associated with the upper surface 14 of the encapsulant12 is a nanolens layer 15. The nanolens layer is designed to redirectlight generated by chips 11 causing mixing of the light. The mixing mayoccur in a number of regions including within the nanolens layer 15,within the encapsulant 12, within a space between the light source and alight guide, or any combination of these regions.

The nanolens layer 15 may be formed by nano imprinting the surface ofthe encapsulant 12 to produce the desired structures, or it may comprisea separate layer of material which has been shaped to have the desiredstructure. This separate nanolens layer will typically be prepared froma transparent polymeric material. Where the nanolens layer is formedseparately, an adhesion promoter may be used to ensure binding to theencapsulant layer. The surface of the nanolens layer 15 will havemultiple light directing structures 16 which redirects the light,causing mixing of the light. While these structures may be dome shapedor hemispherical as shown in FIG. 1, any shape which redirects and/orfocuses light may be used. For example, a frustoconical shape may beemployed.

The encapsulant used in the practice of the invention should beoptically clear and protect the light-emitting diode chips from theenvironment. In one embodiment, epoxy resins are used as theencapsulant, however, other materials, such as silicones may be used.

In an alternate embodiment shown in FIG. 2, another light-directinglayer is used to mix the light. Diffusant 20 is located between theencapsulant 12 and the nanolens layer 15. Diffusant 20 further enhancesthe light mixing. In this embodiment, the light is first mixed by thediffusant layer 20 and then further mixed by the nanolens layer 15. Asshown in FIGS. 2 and 3, the diffusant comprises another nanolens arraythat comprises a lens for each diode chip 10. Note that the lens arraymay comprise more or fewer lens than the number of diode chips. Furthernote that other diffusing structures may be used.

FIG. 3 shows yet another embodiment of the invention. In thisembodiment, reflectors 30 are placed adjacent to the light emittingdiode chips 10 to further enhance the mixing of the light. In thisembodiment the light is first mixed by the reflectors in the encapsulantlayer 12 and then by nanolens layer 15. An optional diffusant layer 20like that described above may also be employed to further mix the light.Note that the reflectors may have other shapes.

Still another embodiment is shown in FIG. 4. In this embodiment, lightdirecting structures are provided on both the outer surface 40 and innersurface 41 of the nanolens layer 15. The shape of the light directingstructures on the inner and outer surfaces may be the same or different.For example, as shown in FIG. 4, dome shaped structures 42 are providedon the outer surface 40 while saw tooth structures 43 are provided onthe inner surface. In this embodiment, the light directing structure onthe outer surface of the nanolens should be capable of directing themixed light into a light guide 44.

As with the embodiments shown in FIGS. 2 and 3, a diffusant layer and/orreflectors may be employed in this embodiment to further enhance lightmixing.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

1. A light source comprising: one or more light-emitting diode chip thatis mounted on a substrate; an encapsulant that at least partiallyencapsulates said chips; and a nanolens layer that is adjacent to anouter surface of said encapsulant.
 2. The light source of claim 1wherein said nanolens layer is imprinted on the outer surface of saidencapsulant.
 3. The light source of claim 1 wherein said nanolens layercomprises a layer of polymer that is associated with the outer surfaceof the encapsulant.
 4. The light source of claim 1 wherein the surfaceof said nanolens layer proximate to said encapsulant comprises at leastone light directing structure.
 5. The light source of claim 1 furthercomprising a diffusant layer that is located between the nanolens layerand the encapsulant.
 6. The light source of claim 1 further comprisingone or more reflectors that are adjacent to said one or more chips. 7.The light source of claim 1 wherein the surface of the nanolens layerdistant from said chips comprises one or more light directingstructures.
 8. The light source of claim 7 wherein said light-directingstructures are dome-shaped.
 9. The light source of claim 1 wherein thenanolens layer comprises: a first surface having a first plurality oflight-directing structures; and a second surface having a secondplurality of light-directing structures.
 10. An optical devicecomprising: a light guide; and a light source associated with a lightentry edge of said light guide wherein said light source comprises: oneor more light-emitting diode chips attached to a substrate; anencapsulant at least partially encapsulating said chips; a nanolenslayer associated with an outer surface of said encapsulant.
 11. Thedevice of claim 9 wherein said nanolens layer is imprinted on the outersurface of said encapsulant.
 12. The device of claim 9 wherein saidnanolens layer comprises a layer of polymer associated with the outersurface of the encapsulant.
 13. The device of claim 9 wherein thesurface of said nanolens layer proximate to said encapsulant comprisesat least one light directing structure.
 14. The device of claim 9wherein the light source further comprises a diffusant layer that islocated between the nanolens layer and the encapsulant.
 15. The deviceof claim 9 wherein the light source further comprises: one or morereflectors that are adjacent to said one or more chips.
 16. The deviceof claim 9 wherein the surface of the nanolens layer distant from saidchips comprises one or more light directing structures.
 17. The deviceof claim 15 wherein said light directing structures are dome-shaped. 18.The device of claim 15, wherein the nanolens layer comprises: a firstsurface having a first plurality of light-directing structures; and asecond surface having a second plurality of light-directing structures.